ELSEVIER Electroencephalographyand clinical Neurophysiology 99 (1996) 440-443 Periodic electroencephalographic pattern in subacute sclerosing panencephalitis modified by preexisting damaged cerebral hemisphere B. Santoshkumar, K. Radhakrishnan* Department of Neurology, Sree Chitra Tirunal Institute for Medical Sciences and Technology, Trivandrum, 695 011, India Accepted for publication: 22 May 1996 Abstract We report a 15 year old girl with a childhood hemiplegia, who developed a recent progressive intellectual decline associated with elevated globulins and measles antibody titres in the cerebrospinal fluid, indicating a diagnosis of subacute sclerosing panencephalitis (SSPE). The magnetic resonance imaging revealed left hemispheric atrophy concordant with a long-standing right hemiplegia, and electroencephalography exhibited lateralized periodic complexes (PCs) over the right hemisphere concordant with left-sided myoclonic jerks. The modification of PCs in our patient due to preexisting damaged cerebral hemisphere illustrate that a fairly functional cortex and subcortical white matter are needed for the expression of the PCs of SSPE. Keywords: Subacute sclerosing panencephalitis; Hemiplegia; Periodic complexes; Electroencephalography 1. Introduction Subacute sclerosing panencephalitis (SSPE) is a slowly progressive fatal inflammatory disease of the central ner- vous system affecting children and young adults (Dyken, 1985). The diagnosis of SSPE can be established if the patient fulfils any 3 of the following 5 criteria (Dyken, 1985): (1) typical clinical presentation with inexorable cognitive decline and stereotyped myoclonic jerks; (2) typical electroencephalographic (EEG) pattern; (3) ele- vated cerebrospinal fluid (CSF) globulin levels; (4) ele- vated CSF measles antibody titres; and (5) typical histological findings in brain biopsy or autopsy. The EEG pattern in SSPE is one of the most character- istic and disease-specific of all EEG patterns (Cobb, 1966; Markand and Panszi, 1975; Miller and Westmoreland, 1983; Westmoreland, 1993). The pathognomonic periodic complexes (PCs) consist of generalized bisynchronous and symmetrical slow waves of high amplitude and a long repetition interval (Cobb, 1966; Markand and Panszi, 1975; Miller and Westmoreland, 1983). However, several atypical EEG findings in SSPE have been documented * Corresponding author. Tel.: +91 471 446069; fax: +91 471 446433; e-mail: sctimst@ren.nic.in (Table 1). The role of preexisting brain disorders in mod- ifying the EEG pattern in SSPE seems to have received little attention. Our report of a patient with SSPE with atypical EEG findings related to preexisting brain lesion is therefore of interest. 2. Case report A 15 year old girl was hospitalized during March, 1995, with a history of progressive cognitive decline of 10 months duration, and myoclonic jerks involving the left side of the body of 4 months duration. She was born full- term after a caesarean section and had normal milestones of development. She suffered 3 episodes of acute bacterial meningitis, secondary to CSF rhinorrhoea, between the ages of 3 and 5 years. The second episode was complicated by the development of a right hemiplegia and aphasia from which she partially recovered in 6 months, but was left with a mild spastic fight hemiparesis. She became left- handed subsequently. She suffered infrequent right simple partial seizures involving fight upper limb and right half of the face, which necessitated treatment with sodium valpro- ate. She was independent in all her activities of daily living and was above average in school performance. The sodium valproate therapy was withdrawn in January, 1994, after a 0013-4694/96/$15.00 © 1996 Elsevier Science Ireland Ltd. All rights reserved PII S0921 - 884X(96)96540-6 EEG 96540